Synastry & Compatibility Calculator - Across 7 Generations Synastry & Compatibility Calculator - Across 7 Generations

Synastry is the astrology of relationships - it compares two birth charts to reveal how two people connect, clash, and complement each other across love, communication, and values.

A synastry chart overlays two people's birth charts to see how one person's planets touch the other's. Horospire builds it across 7 ancestral generations - Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn - scoring how each layer of your lineage harmonises or contrasts with theirs.

You only need each person's birth date to get a synastry score. Adding the birth time and place is optional but recommended: it resolves the timezone and sharpens the fast-moving Moon and other time-based signs, making the comparison more accurate.

Synastry compares two separate charts side by side to see how you interact, while a composite chart blends both charts into one to describe the relationship itself as a third entity. Synastry answers "how do we affect each other"; a composite answers "what is the relationship like".

The calculation uses public-domain astronomical algorithms and Horospire's 7-generation model, so the signs and scores are consistent and repeatable. Treat the results as a reflective, entertainment-and-insight tool for understanding a relationship rather than a deterministic prediction.